1. Field of the Invention
The present invention relates to a vehicular air-bag lid structure.
2. Description of the Related Art
Some vehicles such as automobiles are equipped with air bag systems as a safety device in case of emergency. Such an air bag system is designed to inflate an air bag bodyxe2x80x94that has been folded up and contained in a housing disposed in an instrument panel or the likexe2x80x94toward a person within a vehicle chamber by air pressure from an inflator when an impact exceeding a predetermined value is applied to a vehicle body. At that time, the bag body stops the head of the person seated in the predetermined position so as to prevent his head from hitting the instrument panel and the like.
When the air bag body is inflated, it presses a lid portion formed in the instrument panel to form an inflation opening by cleaving grooves formed in the lid portion, so that the bag body is inflated from the inflation opening toward the person in the vehicle chamber.
The instrument panel has a three-layer structure including an outer skin, a foaming layer and a core material in order from its outer surface side. The instrument panel is formed by setting the outer skin and the core material (which are not shown) in a foaming mold and injecting a foaming agent therebetween to form a foaming layer between the outer skin and the core material.
The air-bag lid portion has a multilayer structure including a door member fitted to an open portion formed in the core material of the instrument panel, a foaming layer (although the foaming layer may be omitted) and an outer skin that are laminated on the door member and continuous to the foaming layer and the outer skin of the instrument panel.
The cleavable grooves may be H-shaped or U-shaped in plan view. The H-shaped cleavable grooves in plan view include a lateral cleavable groove extending in the width direction of the vehicle and a pair of parallel vertical cleavable grooves extending from both the respective ends of the lateral cleavable groove in the longitudinal direction of the vehicle. Each of the grooves passes through the core material and the foaming layer toward the underside of the air-bag lid portion so that it reaches part of the outer skin.
In the conventional vehicular air-bag lid structure, however, the outer skin, for example a vinyl chloride outer skin, of the instrument panel tends to elongate at high temperatures. Moreover, because the door member has been formed so that its whole surface is of substantially uniform strength, it does not function to concentrate force in the center of the lid portion, and does not quickly transmit force to the end portion of each cleavable groove. Consequently, it has been difficult to efficiently break the cleavable grooves.
In the conventional vehicular air-bag lid structure, further, because the lateral cleavable groove crosses the vertical cleavable groovesxe2x80x94in the case of the breaking lines in the H-shape, for examplexe2x80x94stress is concentrated at the intersecting portion between the lateral and vertical cleavable grooves during a heat aging test. Thus, due to this stress concentration, the outer skin may undesirably be broken.
An object of the present invention is to solve the foregoing problems by providing a vehicular air-bag lid structure to an instrument panel or the like, which includes an outer skin, a foaming layer and a core material to ensure that the outer skin of the instrument panel is cloven when door members for inflating the air bag are opened regardless of the temperature which may result in elongation of the outer skin.
Another object of the present invention is to provide a vehicular air-bag lid structure wherein no stress is concentrated in a region where breaking lines of an outer skin are formed.
In order to solve the foregoing problems, a first aspect of the present invention is a vehicular air-bag lid structure having a three-layer structure including: an outer skin, a foaming layer and a core material wherein substantially square door members are fitted to an opening and are activated to be opened via a hinge portion at the time of air bag inflation; a pair of substantially triangular, in plan view, recessed bead portions projecting toward the undersides of the respective door members; and a reinforcing plate accompanying the whole recessed bead portion on the surface side of each door member, each triangular recessed bead portion having two of its sides disposed along the side of a door member and along the side of the hinge portion.
According to the invention, when the outer skin is cloven in the H-shape or U-shape by opening the door member, for example, the door member is smoothly deformed at the time the air bag is inflated so that the strength of the side edge opposite to the hinge portion of each door memberxe2x80x94i.e., the side edge of the lateral cleavable groove portion in the case of H-shaped cleavagexe2x80x94is free from any lateral turning point with the central portion as a peak. In other words, each door member is smoothly deformed when the air bag is inflated, whereby the pressure applied to the outer skin at the time the air bag is inflated is smoothly and laterally changed to ensure that each door member is cloven when each door member is operated regardless of the temperature and the elongation coefficient. Moreover, the surface side of each door member is made flat because its recessed bead portion is covered with the reinforcing plate thereby making substantially constant the wall-thickness of the foaming layer. Thus, the external appearance quality of the lid portion is not deteriorated.
In a second aspect of the invention, the reinforcing platexe2x80x94as set forth in the first aspect of the inventionxe2x80x94is substantially M-shaped so as to singly cover a pair of lateral recessed bead portions.
Further, according to the invention, because the reinforcing plate for covering the pair of the lateral recessed bead portions is a single body, it is easy to produce and fit to each door member.
In a vehicular air-bag lid structure according to a third aspect of the invention, two sheets of opposed door members are provided.
As the two sheets of door members are symmetrically operated to open, the pressure applied to the outer skin of each door memberxe2x80x94when the air bag is inflatedxe2x80x94smoothly deforms the door members three-dimensionally about the central portion of the lateral cleavable line to ensure that the outer skin is surely cloven.
A vehicular air-bag lid structure according to a fourth aspect of the invention includes at least a foaming layer and aH-shaped, inplanview, cleavable line therethrough, the H-shaped cleavable line including a lateral cleavable groove portion extending in the width direction of a vehicle and a pair of parallel vertical cleavable groove portions extending from both ends of the lateral cleavable groove portion in the longitudinal direction of the vehicle, wherein a lateral cleavable groove corresponding to the lateral cleavable groove portion and vertical cleavable grooves corresponding to the vertical cleavable groove portion are formed in the outer skin; and a portion equivalent to the intersecting portion between the lateral cleavable groove portion and the vertical cleavable groove portions in the lateral cleavable groove and vertical cleavable grooves is discontinuous.
According to the fourth aspect of the invention, stress is prevented from concentrating in a portion equivalent to the intersecting portion of the outer skin by making discontinuous the lateral cleavable groove and vertical cleavable grooves. Thus, the outer skin is prevented from being broken during a heat aging test.
A vehicular air-bag lid structure according to a fifth aspect of the invention has at least a foaming layer and a H-shaped, in plan view, cleavable line therethrough, the H-shaped cleavable line comprising a lateral cleavable groove portion extending in the width direction of a vehicle and a pair of parallel vertical cleavable groove portions extending from both ends of the lateral cleavable groove portion in the longitudinal direction of the vehicle, wherein only a lateral cleavable groove corresponding to the lateral cleavable groove portion is formed on the outer skin.
According to the invention, stress is prevented from concentrating in the portion equivalent to the intersecting portion between the lateral cleavable groove portion and the vertical cleavable groove portions by forming a lateral cleavable groove corresponding to the lateral cleavable groove portion. Due to this arrangement, the outer skin is prevented from being broken during a heat aging test.
Because the outer skin needs to have at least a base cleavage point when the air bag body is deployed, the provision of only the lateral cleavable groove portion does not adversely affect cleavage.